Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in CPP):

Solution:
#include <bits/stdc++.h>
#define rep(i,n) for (int i=0; i<(n); i++)
using namespace std;
typedef long long ll;
typedef pair<int,int> P;
const int INF=1001001001;
int dx[4]={1,0,-1,0};
int dy[4]={0,1,0,-1};

int main() {
	int H,W; cin >> H >> W;
	char s[51][51];
	int d[51][51];
	int count = 0;
	rep(i,H)rep(j,W){
		cin >> s[i][j];
		d[i][j]=INF;
		if (s[i][j]=='.')count++;
	}
	queue <P> Q;
	d[0][0] = 0;
	Q.push({0,0});
	
	while (!Q.empty()) {
		int y = Q.front().first;
		int x = Q.front().second;
		Q.pop();
		for (int i = 0; i < 4; ++i) {
			int ny = y + dy[i];
			int nx = x + dx[i];
			if (0 <= ny && ny < H && 0 <= nx && nx < W && s[ny][nx] == '.' && d[ny][nx] == INF) {
				Q.push({ny,nx});
				d[ny][nx] = d[y][x] + 1;
			}
		}
	}
	if (d[H-1][W-1]==INF) cout << -1 << endl;
	//マス目全体の白いマスの個数-けぬす君が通る白いマスの個数
	else cout << count-(d[H-1][W-1]+1) << endl;
	return 0;
}